Heating apparatus of the infrared type are actually used at the present time and are employed for diverse purposes, such as the softening of vehicular roadways, as described in European patent EP-A-0035797, or the heating of small spaces by means of a portable heating apparatus, as described in U.S. Pat. No. 4,452,225. Such apparatus conceived for producing a given quantity of calories at high temperature are particularly suited to their specific application.
Infrared type heating apparatus are also used at the present time for the heating of breeder buildings in the agricultural field, an application for which very specialized apparatus have had to be developed. In effect, the heating of breeder buildings imposes technical constraints which cannot be satisfactorily addressed by the apparatus mentioned above: the production of heat controllable as a function of the zootechnical needs, installation in very dusty atmospheres . . . . To respond to these needs, two principal types of apparatus have been used.
The first type of apparatus comprises primarily a conduit for feeding a gas/air mixture, comprising an air inlet provided with a filter, and a gas injector. This conduit empties into a cylindrical chamber with a refractory grill arranged horizontally below a reflector. In addition, a flame arresting grill is arranged at the inlet of the cylindrical chamber. The control of the heat production is obtained by varying the flow of gas fed to this apparatus which is intended to operate over a very large range of heat output. However, the use of such apparatus has revealed several disadvantages.
Firstly, when the apparatus operates at full power, the chattering noise reflected by the flame is very significant and only abates after a drop in output of about 50%.
Further, the horizontal position of the flame in the torch directs the radiant heat, 50% toward the upper surface of the cylinder and the infrared emission produced by this upper half of the cylinder radiates toward the bottom of the reflector, instead of being directed directly toward the exterior of the reflector. Moreover, when the output diminishes, the flame from the blowpipe preferably touches the upper half of the horizontal cylinder, that is the surface not directed toward the outside of the reflector, and the lower half of the cylinder becomes less and less radiant. Then, if the output diminishes still further, only the upper part of the cylinder near the output tube of the small flame remaining receives a quantity of residual heat which loses, because of the conduction to the entire cylinder, the temperature level necessary for a good luminous infrared emission, even residual. This latter disadvantage is a drawback in the case of certain species of poultry and game birds, which require at the same time as a minimum of radiation, a light reference point to protect them from a gregarious behavior leading to suffocation of a number of them, resulting from stacking up on each other in the darkness.
Finally, this apparatus requires the presence of a filter interposed on the air inlet of the feed conduits, in order to prevent the flame arresting grill from becoming clogged by the aspirated dust. This filter requires a very frequent maintenance in order to avoid its clogging.
The second type of apparatus, described in French patent No. 2,620,799 in the name of the applicant, comes from a different technical field and comprises primarily a reflector in which is integrated a radiant plate of ceramic, associated with a mixing chamber. Such an apparatus offers a very good reliability of operation over a large range of power, and does not present the deficiencies of the apparatus described above. However, this reliability of operation is obtained at the price of a much more sophisticated technology (a pilot light circuit . . . ) than that of the aforementioned apparatus, and as a result an increase of the cost of this type of heating apparatus.
The present invention seeks to overcome the disadvantages of infrared type heating apparatus used for heating of breeder buildings and has as a principal object to provide a heating apparatus of a very simply construction, operating over a very large range of power output, and having, moreover, the peculiarity of remaining emissive of infrared radiation regardless of the level of power.
Another object is to provide a heating apparatus operating without a filter in the air inlet.
Another object of the invention is to provide a heating apparatus permitting obtaining, at the ground and at all levels, an ideal radiation.
Another object of the invention is to provide an easily maintainable heating apparatus, cleanable with water both internally and externally.
Another object of the invention is to provide a heating apparatus which does not generate chattering noise during its operation.